Internal Server Error - file too big?

Nextcloud version 13
Operating system and version Xubuntu 16.04
PHP 5.6
Nextcloud is hosted by “1und1”

The issue you are facing: I try to upload a file with 4,2 GB. The sync runs for over an hour, but at the end appears an Error: Error downloading [filename] - server replied "Internal Server Error (Error while copying file to target location (copied bytes: 1985650688, expected filesize -1)

I tried for three times - every time the same result.
I set the maximum upload size to 16 GB.
Any suggestions?

See this:
Looks like 2G is the limit. Does the server run on a 64bit system?

Hi, I don’t know, on which system the server runs, but there is allready a file with 2,7GB in my Nextcloud - so I think, 2 GB is not the limit.